misc: add fileExists API (#1009)

Author: lauzadis

runtime/runtime-core/api/runtime-core.api

@@ -1583,6 +1583,7 @@ public abstract interface class aws/smithy/kotlin/runtime/util/EnvironmentProvid
 
 public abstract interface class aws/smithy/kotlin/runtime/util/Filesystem {
 	public static final field Companion Laws/smithy/kotlin/runtime/util/Filesystem$Companion;
+	public abstract fun fileExists (Ljava/lang/String;)Z
 	public abstract fun getFilePathSeparator ()Ljava/lang/String;
 	public abstract fun readFileOrNull (Ljava/lang/String;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public abstract fun writeFile (Ljava/lang/String;[BLkotlin/coroutines/Continuation;)Ljava/lang/Object;

runtime/runtime-core/common/src/aws/smithy/kotlin/runtime/util/Filesystem.kt

@@ -31,6 +31,12 @@ public interface Filesystem {
      */
     public suspend fun writeFile(path: String, data: ByteArray)
 
+    /**
+     * Check if a file exists at the [path].
+     * @param path fully qualified path encoded specifically to the target platform's filesystem
+     */
+    public fun fileExists(path: String): Boolean
+
     public companion object {
         /**
          * Construct a fake filesystem from a mapping of paths to contents
@@ -48,4 +54,5 @@ internal class MapFilesystem(
     override suspend fun writeFile(path: String, data: ByteArray) {
         memFs[path] = data
     }
+    override fun fileExists(path: String): Boolean = memFs[path] != null
 }

runtime/runtime-core/jvm/src/aws/smithy/kotlin/runtime/util/PlatformJVM.kt

@@ -48,6 +48,8 @@ internal actual object SystemDefaultProvider : PlatformProvider {
         }
     }
 
+    override fun fileExists(path: String): Boolean = File(path).exists()
+
     public suspend fun readFileOrNull(path: Path): ByteArray? = readFileOrNull(path.toAbsolutePath().toString())
     public suspend fun readFileOrNull(file: File): ByteArray? = readFileOrNull(file.absolutePath)
 

runtime/runtime-core/jvm/test/aws/smithy/kotlin/runtime/util/PlatformJVMTest.kt

@@ -4,15 +4,12 @@
  */
 package aws.smithy.kotlin.runtime.util
 
-import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.test.runTest
 import java.nio.file.Files
 import java.nio.file.Path
 import kotlin.io.path.absolutePathString
 import kotlin.io.path.writeText
-import kotlin.test.BeforeTest
-import kotlin.test.Test
-import kotlin.test.assertEquals
-import kotlin.test.assertNotNull
+import kotlin.test.*
 
 class PlatformJVMTest {
 
@@ -26,7 +23,7 @@ class PlatformJVMTest {
     }
 
     @Test
-    fun itReadsFiles() = runBlocking {
+    fun itReadsFiles() = runTest {
         val actual = PlatformProvider.System.readFileOrNull(tempFile.absolutePathString())
 
         assertNotNull(actual)
@@ -49,4 +46,9 @@ class PlatformJVMTest {
         val allPropertiesFromPlatform = PlatformProvider.System.getAllProperties()
         assertEquals(allPropertiesFromSystem, allPropertiesFromPlatform)
     }
+
+    @Test
+    fun testFileExists() = runTest {
+        assertTrue(PlatformProvider.System.fileExists(tempFile.absolutePathString()))
+    }
 }

runtime/runtime-core/native/src/aws/smithy/kotlin/runtime/util/PlatformNative.kt

@@ -24,6 +24,10 @@ internal actual object SystemDefaultProvider : PlatformProvider {
         TODO("Not yet implemented")
     }
 
+    override fun fileExists(path: String): Boolean {
+        TODO("Not yet implemented")
+    }
+
     override fun osInfo(): OperatingSystem {
         TODO("Not yet implemented")
     }